Let’s say — as an academic proposition and independent of the hand on view — that you require three tricks in a suit where dummy has the J-x-x and you have the A-K-9.

There are only two sensible ways to play this combination. One is to cash the A-K, hoping to find either opponent with the singleton or doubleton queen.

The other way is to lead low from dummy, planning to finesse the nine. This method succeeds when your right-hand opponent has both the queen and ten. Mathematically, it is far better to double-finesse. The A-K will drop the queen only once in every ten deals; the double-finesse will succeed about one time in four.

Jean Besse, Swiss star, was the declarer in this deal from a match against Italy in the European Championship.

He finessed the opening club lead unsuccessfully and got a club return to the ace. After drawing trumps, he cashed the K-A of hearts and ruffed a heart. When he then ruffed a club in dummy, on which West followed with the four, Besse played the A-K of diamonds and caught the queen to make the slam.

Why did Besse abandon the percentage play of the double-finesse? Because he realized that finessing the nine would surely lose and that his only real chance was to drop the doubleton queen.

Besse knew that East had started with exactly two spades, three hearts and six clubs, so that East could not possibly have the Q-10-4 of diamonds (which would give him 14 cards). His only hope, therefore, was that East had started with the Q-4 of diamonds.